Transformation and distribution



(No Model.)

W. J. MQELROY.

TRANSFORMATION AND DISTRIBUTION OI ELECTRIC ENERGY.

No. 392,213. Patented Nov. 6, 1888.

UNITED STATES PATENT TRANSFORMATION AND DiSTRiBUTiON Oi SPECIFICATION ELECTRiC ENERGY.

forming part of Letters Patent No. 392,213, dated November 6, 1888.

Application filed March 12, 1888. Serial No. -267.011. (No model.)

To all whom it may concern.-

Be it known that 1, WILLIAM J. MoELnoY, a citizen of the United States, residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in the Transformation and Distribution of Electrical Energy; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In the transfer of power over considerable distances by means of an electric current the total energy carried may be expressed as the product of two functions of the current, either of which may be raised or lowered without changing the value of said product, provided the other be decreased or increased accordingly, so as to produce a constant resultant. \Ve may realize power from a large current of low potential, expressing such power in terms of the watt, foot-pound, or horsepower, as preferred, by well-known methods; or we may carry a small current of high po tential and obtain the same amount of power as before. As large currents of electricity require large and expensive wires for their con veyance, and as the interest on first cost of the line for such forms an important item of outlay, it follows in the electrical economy that a given amount of power can be more cheaply transmitted by currents of small quantity and high potential carried on small wires than when lower potential, larger currents, and larger wires are used; but such high-tension currents, while cheaply carried, are not so readily applicable to the various uses of electrical power, and their introduction into buildings is a source of danger which militates against their use. It then becomes a most important and desirable object to be able to generate and transmit small currents of high electro-motive force and at the ends of the distributing mains or branches to transfer these currents into others of lower electro-motive force on the service or consumption circuits suitable to the intended purpose; and it is equallyimportant to effect such transfer in such manner as to maintain as closely as possible the total energy of the currents at the resultant figure at which they left the generator. If only'a fall of potential wcrcrcquired at the consumption-points, the problem would be much simplified, since artificial resistance might be introduced and the desired effect attained; but as there would be no augmentation of current strength, but rather a diminution, the loss of available energy or power would be in direct proportion to the fall of potential thus attained.

If, for example, we reduce the elcctro-inotive force on the main by fifty per cent., then fifty per cent. of the initial energy is all we can hope to recover under any circumstances, the other fifty per cent. being expended in a useless heating of the resistances. If, on the contrary, the change can be effected so as to increase the current strength in the same or nearly the same proportion that we reduce the electro-motive force, the maximum economy, efficiency, and safety will be obtained, and to this object my invention is directed.

The invention consists in a system of elec trical distribution by in the details thereof, all substantially as hereinafter more fully described and claimed.

If to one of two metallic sheets or plates separated by a thin sheet of insulating material a charge of electricity be imparted from any source, a charge equal in quality but of opposite sign will be induced on the other plate, and as long as connection with the charging source is maintained these charges will remain on the plates undisturbed. If, now, the charging-wire be removed and the two plates connected together byaconductor, an impulse of current will pass over the wire, electrical equilibrium will be restored,and the charges will disappear, or the same result will follow if both plates be placed to earth. This action and attendant phenomena have long been well known to electricians,and they have adapted the term condenser to a number of such alternating insulated plates.

I have discovered that ifa condenser be introduced into the circuit ofan alternating-current generator the rapid reversal of direct charges on one set of plates will be attended with an equally rapid reversal of induced charges on the other set, and the current in all parts of the circuit will continue as before the introduction of the condenser, notwithmeans of condensers and standing the fact that there is no electrical. contact between the two sides of the condenser and that no flow of current can take place through it in the ordinary sense of the word. The electro-motive force of the current will be unchanged by the introduction of the coudenser or condensers; but the current strength may be materially altered, for, whereasbefore the introduction of the condenser the current strength was regulated by Ohms well-known law, after such changes it will be found to de' pend on the electro-motive force of the generator and the capacities of the condensers their joint capacities if connected in multiple, and the reciprocal or the sum of the reciprocals of their several capacities if arranged in cascade.

1n carrying out my invention I make use of anumber of such condensers in connection with an alternatingcurrcnt dynamo'electric generator and a mainline, and I vary the construction of the condensers from their typical form by making the two groups of sheets of different size, the smaller sheets being connected to the main line, and consequently receiving a charge of high potential, while the larger sheets are connected to the service or local distributing-wires of the system and furnish them currents of electro-motive force suitably low for the desired work. The electro-motive l'orce available for the consumption-circuit is easily regulated or set by the relative sizes of the sheets in the respective sides of the condenser-thc larger the difference the lower the induced electromotive force-and the number of sheets will depend upon the current strength needed for the particular servicewire or circuit supplied. The cause of such change of potential may be readily understoodon reference to at'ew ofthe phenomena of static electricity. If we charge any body ofa given surface to a given potential-say one hundred volts-and then transfer the charge to anothersimilar body of twice the surface,the potential of the charges will be found to have fallen one-half, or to fifty volts. The quantity of the charge is the same as be' fore, but, having spread over double the area, its surface densityis diminished in proportion, and therefore the potential of the charge is re duced by one-half. \Ve know, also, that electrostatic induction produces on one side of any ordinary condenser an induced charge of equipotential and similar amount to thatimparted to the other side.

In constructing my improved condensers I make the sheets, as already stated, of dil'l'erent sizes. For example, if it be desired to carry on the main line a current of one thousand volts and to supply current on the consumption-lines at one hundred volts, then the size of the sheets at one side must be to those atthe other side as one to ten, or nearly so, the smaller sheets being connected to the main line and charged at each pulsation of the generator to five hundred volts on either side of the zero-line. From these smaller sheets charged to this high potential induced charges will be received by thelarger sheets, or rather by those portions of them immediately opposite the smaller sheets, these induced charges being probably of the same initial potential as that shown by the small sheets; but at the instant of reversal of the main current, and just as it swings past the zero-line, the induced eharge,being no longer bound by the electrical attraction of the smaller sheet, is free to flow over asurface ten times larger than that which originally held it, the potential falls to onetenth the original figure, and the electro-motive force at which it can be drawn from this end of the condenser will be correspondingly reduced below that of the inducing'current.

In the drawings herewith, Figure 1 represents a condenser or electrostatic transformer constructed in accordance with my invention. the dielectric layers being represented in solid black. In practice I prefer mica for the dielectric, because of its high specific inductive capacity; but glass, paraftined paper, or other substances may be used. The two sections of the condenser being actually insulated from each other-,no direct circuit exists in the ordinary sense, and any electrical excitation must be entirely due to electrostaticinduction. Fig. 2 is a diagram showing the general plan of my system of distribution of electrical energy applied to incandescent lighting.

A is an alternating-current dynamo-electric generator, and B a small exeiter for the fieldmagncts of machine A. This generator A is ofthe alternating-current type of dynamo, and is wound, for instance, to give a difference of potential between its poles, when running, of one thousand volts. The poles or brushes of such machine when at rest of course are neutral, or, in other words, they are both at the potential of the earth. lVhen such machine is running, at any given instant when the electrical output is at its maximum, the potential of the positive pole will be found to be five hundred volts above the potential of the earth, and the potential of the negative pole will be found to be live hundred volts below the potential of the earth. The difference of poten tial then between the poles will be the normal electro-motive force of the machine-one thousand volts.

The main line 0 starts out from one pole of the generator, the other pole of said generator being connected to earth. At various points where transformation is desired for consumption-eircuits I take off branches or run the main directly to the terminals of the small plates (1 of my improved condensers. The extreme end of the main 0 is left open, as are all endsofbranehes,asshown. Theoppositeterminals-i. 6., those of the large plates 6 of the condensers F-are respectively connected to one side, g, of the consumptioncircuits,which thence passes through the lamps h to the other side, i, of the said consumption-circuits, and thence to earth.

Upon starting the generator A the potential IOC (five hundred volts above the earth or zeroline) developed at one pole is communicated to the main line 0 and the small plates (2 of my condenser-converter. The result on the latter is a disturbance of the electrical equilibrium heretofore existing in the condenser and the development on the large sheets e of a negative charge of equal strength with,but of opposite polarity to, the charge on the smaller sheets, (Z. The condition of the large plates 0, if tested now in comparison with the earth by means of an electrometer, will be found to be five hundred volts below the potential of the earth; but this condition is confined to an area of the larger sheets, 6, equal or about equal to the area of the smaller sheets, (I. As the generator A passes over to its next condition-namely, to that condition when the pole already mentioned exhibits a potential five hundred volts below the potential of the earththere is necessarily a brief interval of time when this pole, the main line 0, and the small sheets (Z of the condenser F are at the same potential as the earth, or, as it is technically known, the deadpoint. Up to this instant the condition of the large sheets 6 has been as follows: The potential on, say, onefifth of their area has been five hundred volts below the earth, the remaining four-fifths being at earth potential. At the instant of dead-point on the main line C and small sheets rl,when the negative charge on the large plates 6 is released, a redistribution of electricity takes place on those plates, and the condition which has been confined to one-fifth of their area spreads over the remainder and is reduced correspondingly in value, and the larger shects,c,no\v present a uniform potential one hundred volts below the potential of the earth. Instantly the earth discharges a current into the large sheets 6, and the electrical equilibrium between the earth and the said sheets is restored. Such current will have an electro motive force of one hundred volts, and hence be suitable for lighting the lamps it to their proper candle-power.

I have here spoken of the discharge of the earth into the large sheets 0 as taking place after the rise in potential of said sheets cfrom five hundred to one hundred volts, but it is only to make the description clear. As a matter of fact, I believe the two operations do occur simultaneously. Thus it will be seen how from one pulsation of the high-tension generator A, I am able to produce in my lampcircuit a pulsation of theproper electro-motive force for incandescent lighting; and it will be still better understood if the next pulsation of the generator A and its attendant static effects be considered.

After passing the dead-point, as described above, the potential of one pole of the machine A falls to a point five hundred volts below the potential of the earth and exhibits the characteristics of what is known as a negative charge. This charged condition extends, of course, as before, to the main line C and the small sheets (Z of the condenser F. Those small sheets (Z, being charged,then,negatively to a potential five hundred volts below the earth-line, induce a positive charge of equal value five hundred volts above the earth-line on the larger sheets, 0, or rather on that por tion of said plates which is immediately opposite the smaller inducing-sheets, (Z. The induced charge, as before, is confined to onefifth of the area of the large plates or sheets e until the pole of the machine A, the main line Qand the small sheets (Z again reach the deadpoint,or line of earth potential, when the five hundred volts charge on the larger sheets, 6, spreads and falls, as before described, to a point where the sheets 0 would show a potential one hundred volts above the potential of the earth; and again electrical equilibrium is restored between the earth and the larger plates, 6, by the discharge this time from the large sheets e through the lamps to earth.

As the polarity of the poles of the generator is reversed many thousands of times per minute, it will be readily understood that the discharges occurring between the condenser and the earth through the lamps it will affect those lamps precisely as would the current from an alternating-current dynamo wound to give an electromotive force of one hundred volts. These lamps may be of different powers, and the electro-motive force required may be varied as desired, since the electrostatic transformers F may be arranged accordingly. The electro-motive force being constant in the consumption-circuits, the volume of current will be in direct proportion to the resistance of the lamps; hence the system in that respect will be self-regulating. Systems of distribution and transformation based upon magnetoelectric induction, or the induction of parallel currents, have to contend with the difficulties of wire resistance and self-inductiou if they are to be made self-regulating, and these difficulties are very grave; but by my system of electrostatic transformation I escape at once from all such complications, and have only the line and branch resistances to contend with-difticulties comparatively trivial-leaving the system the most simple that is possible. Constant difference of potential at the poles of the generator A is all that is needed to secure perfect regulation in the consumption-circuits.

Obviously the invention is susceptible of many modifications, and I therefore do not confine its scope to the specific forms or arrangements shown and described.

Of course, instead of a simple generator of alternating currents, a generator giving asingle-direction current may be employed by using a commutator to alternate the current for the external or inducing circuit. For the purposes of thisinvcntion such an arrangement is properly termed a generator or source of the alternating currents or impulses.

I do not seek in this application to claim the peculiar form of condenser or other appa- ITO inducing an equal potential on the other mem her, then causing the potential to decrease in the latter, and finally discharging it at such decreased potential.

3. The method of transformation of electrical energy, consisting in charging one member of a condenserwith electric potential, thereby inducing potential on the other member, and discharging the latter at a reduced potential.

In testimony whereof I affix my signature in presence of two witnesses.

\VILLIAM J. MCELROY.

\Vitnesses:

T. J. llIoTrGHE, EDITH M'YnRs. 

